Endotracheal tubes are used to couple a patient's respiratory system to a breathing apparatus during surgical procedures or emergency situations. A typical endotracheal tube is made of PVC (polyvinyl chloride), silicone, or similar material and has an inflatable cuff positioned a distance centimeters from an end of the tube that is inserted into the trachea. Thus, the tube can be sealed relative to the trachea by inflating the cuff through an inflation line extending along the endotracheal tube. A fitting on an opposite end of the tube couples the endotracheal tube to an artificial respirator or ventilator.
As is also well known to those skilled in the medical arts, a double lumen endotracheal tube is required in many kinds of thoracic, spine, lung or major vascular surgery when it is necessary to perform single lung ventilation or to ventilate both the left and right lungs separately. A conventional double lumen endotracheal tube provides for individualized ventilation of the two lungs with two lumens each having a cuff positioned about a circumference at proximal (tracheal) and distal (bronchial) locations. The bronchial lumen may extend into either the right or left main bronchus while the tracheal lumen remains in the trachea. The prior art double lumen endotracheal tube is limited by its large diameter which can unfortunately lead to bronchial damage and even vocal cord scarring, especially when it is left in place for a long period of time. Thus, when post-operative ventilation support is anticipated for a patient, the double lumen endotracheal tube is usually removed at the end of the operation and is replaced with a conventional single lumen tube. However, the conventional double lumen endotracheal tube can be associated with significant upper airway swelling due to massive fluid resuscitation during the course of a surgical operation. Under these circumstances, replacement of the double lumen endotracheal tube with a single lumen tube in order to attempt to minimize the aforementioned bronchial damage and vocal chord scarring can be a potentially hazardous and occasionally life-threatening procedure. This is due to the fact that it can be very difficult for an anesthesiologist to see the upper airway and vocal chords adequately to replace the single lumen tube in the swollen upper airway.
Further, it is well known that sudden expiration, such as coughs or spasms, during intubation can cause the bronchi to contract as much as 40 percent in diameter, resulting in substantial compression circumferentially about the bronchial cuff. The prior art cuffs respond appropriately for a smooth, blimp-shaped balloon. The mucus covering of the bronchus and the reaction of its muscles are adapted to expel something the size of the bronchial cuff, which is forced upward, sometimes with sufficient force to cause a bronchial lumen to buckle to force the entire tracheal tube upwards. In such circumstances, the bronchial lumen can be moved into a position so that its terminal opening is moved from the desired bronchus to an undesired location in the trachea or even the other bronchus.
The prior art dual lumen tubes have the following disadvantages when used for one-lung respiration combined with a desired bronchoscope examination of either of the two lungs. (a) Insertion and location of cuffs requires a high degree of skill.
(b) Without being able to see the cuff locations after intubation, it is difficult to keep the bronchial lumen tube fixed at a desired position and the tube often enters deep into or comes out of position during anesthesia.
Prior art non-bronchoscopic dual lumen tubes are shown in U.S. Pat. Nos. 4,453,545 and 4,233,984, where the sole intent of the dual lumen structure is to accomplish selective ventilation of the lungs. Neither of these are adaptable to use with a bronchoscope inserted into one of the lumens. The '948 patent device provides a lumen separation which is intended to respond with side to side collapse with a very minor pressure difference. The '545 patent describes that the FIG. 2 device is simply not stable and teaches away from its use in favor of a relatively small diameter bronchial lumen tube with an enlarged cuff. The enlarged cuff lacks position-maintaining tube support which might preserve its location in the lung.
Referring again to surgical environments where dual lumen tube respiration is desired, it is well known that surgery involving the lung or the contents of the thorax often requires cessation of ventilation to one lung to keep the lung immobile while surgery on it is performed or to deflate the lung for better visualization of thoracic structures. Other indications for lung isolation include: containment of unilateral pulmonary bleeding or infection and management of bronchopleural fistula or other pulmonary air leaks. The generally accepted prior art solution for lung isolation is the double lumen endotracheal tube. Modern disposable plastic double lumen tubes are modifications of the original Robert-Shaw tube introduced more than sixty years ago. These endotracheal tubes contain two separate lumens, one for each lung, and ventilation is separated with the use of endotracheal and endobronchial balloon cuffs. The DLT design suffers from two major drawbacks that negatively affect clinical care. The first is the large size of the tube, namely its effective diameter and cross-sectional surface area. Current adult sized double lumen tubes are typically 35-41 French in external circumference; this large size is needed to accommodate the necessary plastic structure (extruded walls) and ventilation passages. Aside from being large, the double lumen tubes are also relatively stiff due to the plastic material used in their construction. The combination of their large and bulky design and undesired stiffness can lead to difficult insertion and even airway injury. Even if insertion is atraumatic, the double lumen tubes' large external diameter increases the pressure on the glottic opening, potentially injuring these delicate structures, especially during prolonged intubations.
The second major design drawback to the prior art double lumen tubes is the relatively small size of the ventilation passages. Even the current prior art double lumen tubes have large external diameters, resulting in a bulky design to house two relatively small diameter channels, thus limiting the size of bronchoscopes, suction catheters, and other instruments that could be inserted into the lungs during use. No adult double lumen tube sizes (35-41 Fr) can accommodate a pulmonary bronchoscope needed to perform diagnostic or therapeutic bronchoscopy (minimum 4.9 mm O.D.). If a diagnostic or therapeutic bronchoscopy exam is to be performed (suction/lavage, bronchial biopsy, bronchial laser) prior to surgical lung resection, a standard large bore endotracheal tube must first be utilized for this part of the procedure to accommodate the large bore bronchoscope. Once the bronchoscopy is completed, the endotracheal tube must be removed and a separate double lumen tube must be inserted in its place, a procedure that is often fraught with risk. A limited lumen diameter imposed on double lumen tubes poses a special clinical challenge when a patient is bleeding from one lung, and lung isolation is warranted. Although a double lumen tube is ideal for lung isolation to prevent flooding the good lung with blood, placement of a double lumen tube severely limits one's ability to perform the diagnostic and therapeutic bronchoscopy necessary to treat this medical emergency.